CN103654766A - Low-override amplification device for weak physiological signals - Google Patents
Low-override amplification device for weak physiological signals Download PDFInfo
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- CN103654766A CN103654766A CN201310567024.0A CN201310567024A CN103654766A CN 103654766 A CN103654766 A CN 103654766A CN 201310567024 A CN201310567024 A CN 201310567024A CN 103654766 A CN103654766 A CN 103654766A
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Abstract
The invention provides a low-override amplification device for weak physiological signals. The low-override amplification device comprises an on-line impedance detection network module (1), a low-override direct-current amplification module, a signal collecting and converting module (2), an electromagnetism isolation module, a data transmission module (7), a signal processing unit (13), a display module (14) and a detection electrode (11).
Description
Technical field
The present invention relates to a kind of weak physiological signal low range amplifying device.
Background technology
Clinical and the research of extensive use of physiological signal extractive technique, but there is following shortcoming in it: 1. signal extraction adopts to exchange and amplifies, and makes to extract frequency band and is restricted, and is unfavorable for studying the essence of signal.2. current, signal extraction adopts channel switching technology, makes channel isolation low; The factor of direct current saltus step and AC coupled, lengthens signal stationary time.Be embodied in: the skin physiology signal of telecommunication has that frequency is low, amplitude is weak, output impedance greatly, the feature that is easily disturbed, to extracting amplification system, have higher requirement.As electrocardiosignal, amplitude is 10uV mono-5mV, and frequency is 0.05～100Hz, so be very easily subject to the impact of environment.EEG signals is than also weak 100 times of electrocardios, generally only have 50 μ V left and right, amplitude range is 5 μ V～100 μ V, frequency is divided δ wave band ((1-4Hz), θ wave band (5-7Hz), α-1 wave band (8-10Hz), α-2 wave band (11-12Hz, β-1 wave band (13-18Hz), β-2 wave band (19-31Hz) and γ wave band (being greater than 31HZ).Traditional physiology electric amplifier architecture is buffer stage, instrument amplifier stage, high-pass filtering level, main amplifier stage, low pass filtered wave scale.Wherein main amplifier stage, is generally multistage amplification, needs amplifier quantity many, and power consumption increases, system reliability reduces, noise introducing approach is many.
Summary of the invention
The present invention proposes a kind of low range amplifying device based on direct current amplification and parallel acquisition, this device changes at present general physiological signal and gathers amplification mode, the direct current amplifying technique that is low to moderate 20 times in the utilization of physiological signal collection front end is carried out signal amplification, retain most possibly weak physiologic information, use multi-channel parallel acquisition technique, realize and really do not have passage to switch the time domain phase transformation bringing, by mathematical calculation, realize software common mode rejection ratio.Secondly by digital filter, its advantage is that degree of stability is high, high conformity, signal are synchronous.In addition, the composition of system reduces number of devices, and power-dissipation-reduced, EMC performance are good, and system is more reliable.Use one-level direct current to amplify, all information is all gathered, design accurate digital filter and digital differential algorithm, extract useful physiological signal.This one-level direct current amplifies and high-resolution modulus conversion technique, for parallel multi-channel physiological signal provides possibility.This designing technique, has saved a large amount of amplifiers, has reduced capacitance resistance ware simultaneously, has reduced power consumption, and circuit noise has reduced introducing approach, and certain limit has improved signal to noise ratio.
For achieving the above object, weak physiological signal low range amplifying device of the present invention comprises: online impedance detection mixed-media network modules mixed-media (1), low range direct current amplification module, signals collecting modular converter (2), electromagnetic isolation module, data transmission module (7), signal processing unit (13), display module (14), detecting electrode (11), it is characterized in that: described detecting electrode (11) is physiological signal sensor, whether described online impedance detection mixed-media network modules mixed-media is realized fully and being contacted with skin for detection of described detecting electrode (11), to determine whether to carry out the collection of physiological signal, described low range direct current amplification module comprises unipolarity direct current amplification module (9) and bipolarity direct current amplification module (10), described unipolarity direct current amplification module (9) is for amplifying gathered EEG signals, described bipolarity direct current amplification module (10) is for amplifying gathered electrocardiosignal, described signals collecting modular converter (2) comprises a plurality of D/A converter module A/D and the first CPU (22), described a plurality of D/A converter module is for being converted to digital signal by the analogue signal of collection, then after processing, the first CPU (22) is sent to described data transmission module (7), described electromagnetic isolation module is used for realizing the bi-directional electromagnetic isolation between signal acquisition module (2) and data transmission module (7), described data transmission module is sent to respectively signal processing unit (13) and display module (14) by the signal receiving.
Described, between detecting electrode and skin, increase conductive paste or carry out skin surface processing, to reduce contact resistance.
Described detecting electrode comprises Ag or AgCl electrode.
The quantity of described a plurality of D/A converter modules is 40, can carry out synchronous acquisition by Dui40 road signal, realizes batch total calculation mutually between signal.
Described data transmission module comprises high speed USB 2.0 data transmission modules, and it is CY7C68013 interface chip, the transmittability of its tool 480MHz.
Described data transmission module 7 is connected by RS232 with display module (14).
Described signal acquisition module (2) has the port of output PWM, and the pwm signal of exporting is converted to the sinusoidal signal for online impedance detection mixed-media network modules mixed-media after over level conversion unit (8).
Described electromagnetic isolation module comprises magnetic isolation module (5) and electric isolation module (6).
The clock frequency of described D/A converter module is 7.168MHz.
In order further to understand feature of the present invention and technology contents, refer to following about detailed description of the present invention and accompanying drawing, yet accompanying drawing only provide with reference to and explanation use, be not used for the present invention to be limited.
Accompanying drawing explanation
Below in conjunction with accompanying drawing, by the specific embodiment of the present invention is described in detail, will make technical scheme of the present invention and other beneficial effect apparent.
Fig. 1 is the composition schematic diagram of the weak physiological signal low range amplifying device of the present invention;
Fig. 2 is unipolarity amplification module homophase structure for amplifying schematic diagram;
Fig. 3 is the electric principle schematic of unipolarity amplification module;
Fig. 4 is the amplification principle schematic diagram of instrument amplifier AD620;
Fig. 5 is the amplification principle schematic diagram of bipolarity amplification module;
Fig. 6 is the circuit structure diagram of online impedance detection mixed-media network modules mixed-media.
The specific embodiment
Technological means and the effect thereof for further setting forth the present invention, taked, be described in detail below in conjunction with the preferred embodiments of the present invention and accompanying drawing thereof.
As shown in Figure 1, weak physiological signal low range amplifying device of the present invention comprises: online impedance detection mixed-media network modules mixed-media 1, low range direct current amplification module, signals collecting modular converter 2, electromagnetic isolation module 5 and 6, data transmission module 7, signal processing unit 13, and display module 14.
This device also comprises Ag or AgCl detecting electrode 11, is also physiological signal sensor.The quality of the physiological signals such as the affects brain electricity of electrode one contact skin impedance, electrocardio, excessive easy introducing 50Hz disturbs, and the amplitude of physiological signal also reduces.Online impedance detection is by applying alternating current to electrode one skin contact, and the voltage signal of detecting electrode one skin contact reaction, calculates R=U/I.If impedance is excessive, will increases conductive paste or carry out skin surface processing (using sand papering horny layer), to reduce contact resistance.This before offical record, directly objectively observe contact impedance, ensured the signal to noise ratio of tracer signal.
Whether online impedance detection mixed-media network modules mixed-media 1 is realized fully and being contacted with skin for detection of Ag or AgCl detecting electrode 11, to determine whether carry out the collection of signal.The sinusoidal signal that dependence is provided by signals collecting modular converter 2 and level conversion unit 8 can be stable realize this detection.The detection of using sinusoidal signal to contact belongs to the content of prior art, at this, need not be described in more details.The circuit structure of online impedance detection mixed-media network modules mixed-media as shown in Figure 6.
Low range direct current amplification module comprises unipolarity direct current amplification module 9 and bipolarity direct current amplification module 10, and direct current amplifies, and the physiological signal that has reacted wider can record, the more realistically composition of reaction signal.Next is avoided resembling exchanging and amplifies because of the inconsistent distorted signals of bringing of resistance-capacitance network parameters precision.Homophase direct current amplifies, and has improved the input impedance of amplifier.Electro-physiological signals generally picks up by metal, when with contact skin, can produce polarization DC potential, generally more than hundred mV, and analog digital conversion scope ± 2.5V, thereby adopt low range to amplify.Low range is amplified, and the stability of amplification system is high, and reaction is fast, there is no AC amplification time constant.Unipolarity direct current amplification module 9 is wherein for amplifying EEG signals, and bipolarity direct current amplification module is used for amplifying electrocardiosignal.
Low range unipolarity amplification principle: unipolarity amplifier generally adopts homophase structure for amplifying, as shown in Figure 2.Homophase amplification has the advantages that input impedance Rin is high, is suitable for the physiological signal high to source impedance.
Amplification
So, the noise of circuit and the selected amplifier of setovering out determine.In order to save power consumption, can be applicable to USB interface powering mode, the OP497 with accurate pA input current characteristics that selects AD company to produce.
Its feature is:
open-loop gain: 2000V/mV minimum
electric current: 625 μ A maximum
Its electric principle as shown in Figure 3.From schematic diagram, know, amplification is 19 times.Physiological signal amplitude is generally below mV level, and polarization potential is more than hundred mV, and visible signal to noise ratio is very poor.In order to obtain useful physiological signal in the situation that signal-to-noise performance is very low, necessary design resolution, at the following AD of uV, is processed in digital field.
Low range bipolarity amplification principle:
Bipolarity is amplified can effectively improve common mode rejection ratio, common-mode signal is curbed at system front end, especially polarization potential and 50Hz interfering signal.General physiology amplifier all adopts bipolarity to amplify.Its principle as shown in Figure 4.The input buffer amplifier of instrument amplifier passes through common-mode signal with unit gain (or low gain).On the contrary, two buffer amplifying signal voltages.From the output signal of two buffers, be connected to the subtractor unit of this instrument amplifier.(conventionally with low gain or unit gain) amplified difference signal here, and decay (representative value is 10,0001: or more than) common-mode voltage.
Select instrument amplifier AD620 to make bipolar amplifier.Its amplification principle as shown in Figure 5.From figure, know,
the same with unipolarity amplifier, bipolar amplifier only suppresses common-mode signal, and difference mode signal is amplified, and can effectively suppress polarization potential and 50Hz common-mode signal, can effectively improve signal to noise ratio.In like manner, bipolarity amplify to adopt direct current to amplify, effective institute's composition of inhibit signal, and distorted signals is less.
The present invention adopts low range direct current amplification module respectively electrocardio and EEG signals to be amplified, and then the signal after amplifying is processed in signal processing unit 13, has omitted high pass filter of the prior art.
Signals collecting modular converter 2 comprises 40 A/D (analog-digital converter) 3, can carry out synchronous acquisition by Dui40 road signal, really realizes batch total calculation mutually between signal.As signal calculated difference, signal and center altogether, the function such as event channel derivation.Adopt the form of daisy chain that 40 AD are composed in series, same clock, enabling signal, reset signal, reference source have ensured analog-to-digital concordance.Certainly, wherein the quantity of A/D is not limited in 40, can be also other quantity.Clock frequency is wherein 7.168MHz.This signals collecting modular converter also comprises CPU 22, is provided with serial peripheral equipment interface SPI 23 and pulse width modulating signal PWM output port 21 in CPU.Wherein SPI23 is for receiving the signal after being changed by A/D converter, the output signal of PWM port 21 becomes stable sinusoidal signal after the conversion of over level conversion unit 8, and this sinusoidal signal is for realizing online impedance detection mixed-media network modules mixed-media 1 for the contact detection of electrode.
In the present invention, with the form of software, produce the square-wave signal of pulse width modulation, this square-wave signal is transformed to become from level conversion unit 8 again can be for the stable sinusoidal signal of online impedance detection mixed-media network modules mixed-media 1, with respect to prior art, use independent sine wave generator chip, can reduce the load of system and reduce costs thus.
Between signals collecting modular converter 2 and data transmission module 7, use magnetic isolation module 5 and electric isolation module 6 to realize the two-way isolation of electromagnetism between module 2 and module 7.
Data transmission module 7 comprises CPU 71 and high speed USB 2.0 data transmission modules 73, this module 73 is CY7C68013 chip, it is a high performance USB2.0 interface chip, has high speed, GPIF interface, FIF0 interface, feature easy to connect.This data transmission module 73 is realized and signal processing unit 13 by USB4.And the transmission performance of its 480MHz, has greatly met 40 and has led above transfer of data.This module 7 also comprises RS232 port 74, for realizing and being connected of display module 14.
Described high pressure magnetic isolation module 5 uses the i Coupler technology of AD company, substitutes traditional light Rhizoma Nelumbinis isolation.Have speed high, interface circuit is simple, the feature that isolation voltage is high.We select ADuM2200/ADuM2201, and its feature is:
High isolation: 5000V rms
Safety criterion: IEC61000-4-x
Low-power consumption: 5V operation
1.6mAper?channel?maximum@0Mbps?to2Mbps
3.7mAper?channel?maximum@10Mbps
3V?operation
1.4mA?per?channel?maximum@0Mbps?to2Mbps
2.4mA?per?channel?maximum@10Mbps
Communication pattern: two-way communication
Adapt to 3V/5V level conversion
The hardware technology index that this device reaches is as follows:
resolution: 22bit;
The above; for the person of ordinary skill of the art; can make other various corresponding changes and distortion according to technical scheme of the present invention and technical conceive, and all these changes and distortion all should belong to the protection domain of the accompanying claim of the present invention.
Claims (9)
1. physiological signal low range amplifying device a little less than a kind, comprise: online impedance detection mixed-media network modules mixed-media (1), low range direct current amplification module, signals collecting modular converter (2), electromagnetic isolation module, data transmission module (7), signal processing unit (13), display module (14), detecting electrode (11), it is characterized in that: described detecting electrode (11) is physiological signal sensor, whether described online impedance detection mixed-media network modules mixed-media is realized fully and being contacted with skin for detection of described detecting electrode (11), to determine whether to carry out the collection of physiological signal, described low range direct current amplification module comprises unipolarity direct current amplification module (9) and bipolarity direct current amplification module (10), described unipolarity direct current amplification module (9) is for amplifying gathered EEG signals, described bipolarity direct current amplification module (10) is for amplifying gathered electrocardiosignal, described signals collecting modular converter (2) comprises a plurality of D/A converter module A/D and the first CPU (22), described a plurality of D/A converter module is for being converted to digital signal by the analogue signal of collection, then after processing, the first CPU (22) is sent to described data transmission module (7), described electromagnetic isolation module is used for realizing the bi-directional electromagnetic isolation between signal acquisition module (2) and data transmission module (7), described data transmission module is sent to respectively signal processing unit (13) and display module (14) by the signal receiving.
2. device as claimed in claim 1, is characterized in that, increases conductive paste or carries out skin surface processing, to reduce contact resistance described between detecting electrode and skin.
3. device as claimed in claim 1, is characterized in that, described detecting electrode comprises Ag or AgCl electrode.
4. device as claimed in claim 1, is characterized in that, the quantity of described a plurality of D/A converter modules is 40, can carry out synchronous acquisition by Dui40 road signal, realizes batch total calculation mutually between signal.
5. device as claimed in claim 1, described data transmission module comprises high speed USB 2.0 data transmission modules, it is CY7C68013 interface chip, the transmittability of its tool 480MHz.
6. device as claimed in claim 1, described data transmission module 7 is connected by RS232 with display module (14).
7. device as claimed in claim 1, described signal acquisition module (2) has the port of output PWM, and the pwm signal of exporting is converted to the sinusoidal signal for online impedance detection mixed-media network modules mixed-media after over level conversion unit (8).
8. device as claimed in claim 1, described electromagnetic isolation module comprises magnetic isolation module (5) and electric isolation module (6).
9. the device as described in claim 1 or 4, the clock frequency of described D/A converter module is 7.168MHz.
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Cited By (2)
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| CN105997060A (en) * | 2016-05-09 | 2016-10-12 | 中国航天员科研训练中心 | An electroencephalogram analysis system used in an electromagnetic radiation environment |
| TWI681754B (en) * | 2018-08-02 | 2020-01-11 | 逢甲大學 | Monopolar physiological signal detection device and its operating method |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105997060A (en) * | 2016-05-09 | 2016-10-12 | 中国航天员科研训练中心 | An electroencephalogram analysis system used in an electromagnetic radiation environment |
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| US10888233B2 (en) | 2018-08-02 | 2021-01-12 | Feng Chia University | Monopolar physiological signal detection device and its operating method |
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Application publication date: 20140326 |